5. FILES › 5.2 VTOC/Catalog Activity Information Area Files › 5.2.1 Data Set Allocation File (VCADAA) › 5.2.1.3 VCADAA Usage Considerations

5.2.1.3 VCADAA Usage Considerations

This section identifies any special considerations or
techniques related to using the VCADAA file.


Relationship to Data Sources from VCC

VCADAA is built from the data in the VTOC. As such, it
contains observations for all data sets on scanned primary
storage including VSAM and any DFHSM ML1 data sets (present
only if ML1 volumes are not EXCLUDED).

While it contains observations for VSAM data sets, none of
this data comes from the catalog structures -- only the
VTOC. For details on VSAM data sets, use the VCA_VS file.

While it may contain observations for data sets under DFHSM
management, none of this data comes from the DFHSM MCDS or
BCDS -- only the VTOC. For details on inactive data sets or
backup versions, use the HSMMIG and HSBBAC files
respectively.

VCADAA Is the Preferred Source For Accounting

We recommend using the VCADAA file when accounting for
primary DASD occupancy. The VCADAA file is valid for
accounting for both VSAM and non-VSAM.  Because the VTOC is
the definitive source of what is allocated, it follows that
space allocated (DAAALLSP) and its DURATION-oriented
derivatives (DAADURSP or DAAKBHR) are always most accurate
with the VTOC as a data source.

Note that the above statements only apply to VSAM data sets
cataloged in ICF catalogs. Suballocated objects cataloged in
pre-ICF catalogs require the VSAM-only view offered by the
VCA_VS file.

Therefore, if you do not have any pre-ICF catalogs still in
use (that is, all your catalogs are ICF), then the VCA_VS
file should only be used for accounting if fields in the
VCA_VS file and not in the DAA file are required.  Use the
VCADAA file instead and consider keeping a few cycles of the
VCA_VS at DETAIL only for VSAM studies of performance.

Last-Reference-Date (DAAREFDT) for VSAM and Non-VSAM

VCADAA is the proper source of information for last date
referenced (DAAREFDT). While an identically-named variable
exists in the VCA_VS file, only the VCADAA file is accurate
because MVS only maintains the date last referenced
information in the VTOC.

Beginning with DFP Version 3, the maintenance of last
reference date in the VTOC is automatic. If your DFP level is
below DFP Version 3, you will need to either install DFHSM or
several IBM APARs to capture date of last reference for all
access methods.

Significance of DAADSTYP Indicator

DAADSTYP identifies the general type of data set:

     OS for non-VSAM
     VS for VSAM
     HS for a DFHSM-managed object
     HV for a DFHSM-owned VSAM SDSP

Historically, it has been included as a SORT/SEQUENCE
variable causing summarization breaks at the DAYS timespan
and higher.

Try to avoid using DAADSTYP in your VCAACRT routine since
this variable will not be available for the HSMMIG and
HSBBAC files.

Observations for VSAM Data Sets

The DETAIL VCADAA file reflects the actual allocated space
used by a VSAM Relative Record Data Set (RRDS), Entry
Sequenced Data Set (ESDS), Key Sequenced Data Set (KSDS), or
Linear Data Set (LDS).  Each VSAM data component (and each
KSDS key range data component) has an observation for every
volume occupied by the VSAM data set.  In addition, all KSDS
structures have a second set of observations (one per volume)
to identify the index component.

Note that there are no observations for CANDIDATE volumes.
Candidate volumes are specified when the VSAM data set is
defined.  They are used only after the data set fills its
primary and secondary allocations on the prime volumes.
Candidate volumes are no longer supported (needed) in a DFSMS
environment.

The first thing that you will note about VSAM data sets in
the DETAIL timespan of the VCADAA file is that Space Used
(DAASPACU) is equal to Space Allocated (DAASPACA).  The
second is that there are very few elements describing VSAM
data sets.

One other important thing to remember is that only the data
set names for the DATA and INDEX components are present; you
will not find the cluster name in the VCADAA file.
Furthermore, for key range defined VSAM data sets, the DATA
and INDEX component names (DSNAME) will be suffixed by a
unique four-character qualifier (a letter from A-Z followed
by a three-digit sequence number).

Extra Observations If Greater Than 16 Extents (VSAM)

Because a VSAM data set may have 128 extents and an
observation will only hold 16 extents, pseudo observations
can be created to represent this additional level of detail
about the data set.

Please refer to Section 5.2.2.3 where this is discussed in
detail.

Multi-Volume Effect On Reporting

To report on the whole VSAM data set you will need to sort
(and possibly summarize) the VCADAA file by Data Set Name
(DSNAME) followed by Volume Serial Number (VOLSER) to bring
the various parts together.